The present invention relates generally to the maintenance and rehabilitation of water wells and specifically to systems and methods for monitoring the change in permeability of the well structure (e.g., screen, gravel pack, and geological formations) surrounding boreholes which can influence the water production capability of water wells.
Bore holes are commonly drilled into the ground in order to locate and extract water from water-bearing geological formations. Specifically, the bore hole allows the extraction of ground water from intergranular pore spaces, fractures and cavities that naturally occur in various geologic formations. Screens, gravel packs, and other structures can be inserted into the bore hole in order to create a well structure. The inherent ability of the well structure to transmit ground water is known as hydraulic conductivity or permeability. Well structures, whether vertical or horizontal, provide a method for the water to collect and be accessed. Various types of pumps can be installed in wells to extract the water or other liquids. Over time, the side walls of the well structure can become clogged or contaminated with matter, thereby inhibiting the ability of the water to flow into the borehole. In order to alleviate this problem, the side walls of the well structurecan be cleaned in order to remove the clogging and/or plugging matter. One such way of removing the clogging and/or plugging matter is by a system known commercially as Airburst® available from Airburst Technology, LLC of Muskego, Wis. The basic principles of this technology are disclosed in U.S. Pat. No. 5,579,845, which is hereby incorporated by reference in its entirety.
In order to determine whether or not existing well-cleaning systems are effective, it is also known to install a pump in the well after cleaning to determine any changes in the permeability of the well, such as by measuring the specific capacity (gallons per minute per foot of liquid drawdown) of the well and thus determine the effectiveness of the cleaning process. This requires removal of the cleaning equipment and can involve many hours or days of intensive labor to install the pump. If it is determined by pumping that additional cleaning is required, the pump must be removed and the cleaning equipment reinstalled in the bore hole. This time and labor consuming procedure is undesirable as an intermediate step in the cleaning process.
It is also known to insert a video camera into the well after the cleaning operation. This commonly involves removing the cleaning apparatus and then inserting the video camera into the well to visually determine the effectiveness of the cleaning operation. It is also known to position the video camera in the well along with the cleaning apparatus so that removal of the cleaning apparatus is unnecessary. In either case, the use of a video camera relies on visual verification of the cleaning operation, which is not the most accurate way to determine the effectiveness of a cleaning operation. In addition, one must wait for the clogged and/or plugged matter in the well (which was removed during the cleaning operation) to settle to the bottom of the well so that the video camera can clearly see the sidewall of the well structure and visually determine the effectiveness of the cleaning operation. This waiting period is undesirable.